The present invention relates to articles and methods for imparting softening and anti-static benefits to fabrics in an automatic laundry dryer. More specifically, damp fabrics are commingled with a softening composition containing cationic fabric softener and a "sorbitan ester" component in an automatic clothes dryer to provide a soft, antistatic finish concurrently with the drying operation. The softening compositions herein are employed in combination with a dispensing means adapted for use in an automatic dryer. The sorbitan ester not only provides fabric softening but also serves to improve release of the softening composition from certain types of dryer dispensing means. Furthermore, the sorbitan ester materials herein, when employed in combination with conventional cationic fabric softening agents in a laundry dryer, provide antistatic performance superior to that obtained when either cationic materials or sorbitan ester materials alone are used in the dryer.
Fabric "softness" is an expression well-defined in the art and is usually understood to be that quality of the treated fabric whereby its handle or texture is smooth, pliable and fluffy to the touch. Various chemical compounds have long been known to possess the ability to soften fabrics when applied to them during a laundering operation.
Fabric softness also connotes the absence of static "cling" in the fabrics, and the commonly used cationic fabric softeners desirably provide both softening and antistatic benefits when applied to fabrics. Indeed, with fabrics such as nylon and polyester, the user is more able to perceive and appreciate an anti-static benefit than a true softening benefit.
Fatty alkyl cationic anti-static softening compounds and compositions designed for application to fabrics in an automatic dryer have been the subject of recent innovations. (See, for example, Furgal, U.S. Pat. No. 3,634,947, issued Jan. 18, 1972; Morton, U.S. Pat. No. 3,686,025, issued Aug. 22, 1972 and Gaiser, U.S. Pat. No. 3,442,692, issued May 6, 1969.) Other fatty materials have been suggested for use as dryer-added fabric softeners (See, for example, Hewitt et al, U.S. Pat. No. 3,676,199, issued July 11, 1972 and the co-pending application of Murphy and Habermehl, Ser. No. 417,329, filed Nov. 19, 1973). Included among these prior softening compositions are various glycerides in combination with oil-soluble, lower-ethoxylated surfactants. Triglyceride fabric treating agents are disclosed in Bernholz et al, U.S. Pat. No. 3,785,973, issued Jan. 15, 1974.
As pointed out in Hewitt et al, U.S. Pat. No. 3,676,199, issued July 11, 1972 and Wixon, U.S. Pat. No. 3,766,062, issued Oct. 16, 1973, many of the prior art softening agents stain or discolor the conditioned fabrics when used in an automatic dryer. The unfortunate tendency of such materials to stain fabrics is apparently caused by the presence of the fatty alkyl groups in the active softening compounds which causes them to be somewhat "greasy." Unevenly distributed fatty softeners can appear as blotchy, oily stains on the treated fabrics. Thus, the chemical structure which gives rise to the soft, lubricious feel associated with the prior art softeners can cause them to be potential fabric stainers.
A variety of mechanical methods have been employed in an attempt to reduce the tendency of dryer-added softeners to stain fabrics. The prior art fabric softening agents, for example, have been sorbed onto flexible articles designed to provide controlled release at dryer operating temperatures. While such articles are quite attractive from the standpoint of ease of manufacture and economics, staining can still be a problem if an improperly formulated flexible article becomes entangled in clothing. Various rigid dispensers and appliances have been designed which assertedly avoid any exceptionally high, localized concentration of softening agent being undesirably deposited on the fabrics in the form of greasy stains (See Hoeflin, U.S. Pat. No. 3,633,538, issued Jan. 11, 1972 and Grand et al, U.S. Pat. No. 3,698,095, issued Oct. 17, 1972). However, such dispensers are costly and have not come into general use.
Certain surfactants have been suggested for obviating the tendency of the prior art softeners to stain fabrics (See the co-pending application of Murphy and Habermehl, Ser. No. 440,932, filed Feb. 8, 1974). This nonstaining aspect is especially important when the common polyester fabrics, which are oleophilic and particularly susceptible to oily staining, are softened in an automatic dryer. However, such surfactants are mainly anionic in nature, and are not suitable for use with the common cationic softeners.
As noted above, many softening compounds have been adapted for use in automatic dryers by fashioning articles which contain a pre-measured amount of the softener. Preferred articles comprise a flexible sheet substrate coated and/or impregnated with an optimal, pre-measured amount of a fabric softener. These articles are simply added to a dryer together with the fabrics to be dried. The heat and tumbling action of the dryer helps dispense the softener onto the fabric surfaces (See for example, Perez-Zamora, U.S. Pat. No. 3,632,396, issued Jan. 4, 1972). However, once sorbed onto the sheet substrate, some softeners tend to remain affixed thereto, rather than being dispensed onto the fabrics. Thus, the user of such articles cannot be assured that the optimal amount of softener is, in fact, deposited on the fabrics. To obviate this problem, it has been suggested to layer the softener onto the sheet together with surfactant-type release agents which insure substantially complete transfer to the fabrics; (See Perez-Zamora, U.S. Pat. No. 3,632,396, issued Jan. 4, 1972). However, the sorbitan esters do not appear to have been recognized as being useful for this purpose.
Finally, some cationic materials recognized for use as fabric softeners and anti-static agents in dilute aqueous rinse baths are not particularly useful in certain automatic dryers in that they are reported to soften and loosen certain paints used to protect the dryer drum and to corrode exposed metal surfaces of some automatic dryer drums.
As can be seen from the foregoing, there is considerable interest in providing reduced staining fabric softeners which can be conveniently applied to fabrics in an automatic clothes dryer. Moreover, the difficulty in securing controlled softener release from dispensers are well-recognized by workers in this field. Finally, there is likewise considerable interest in eliminating or minimizing dryer paint softening and corrosion caused by some dryer-added fabric treating products.
By the present invention, minor amounts of fatty esters of certain poly-ols, i.e., the so-called "sorbitan esters," are added to cationic fabric softeners to provide particularly useful dryer-added fabric softener compositions and articles. The sorbitan esters provide auxiliary softening and antistatic treatment of fabrics in addition to that provided by the cationic softeners. Moreover, the sorbitan esters provide improved release of softening compositions from carrier substrates when such substrates provide the means for dispensing the softening compositions herein into automatic dryers. Finally the particular fabric treating materials utilized in the present invention do not disadvantageously interact with dryer paint or exposed metal surfaces of dryer drums.
Various compounds containing hydroxyl groups are recognized as useful fabric treating agents in aqueous media, e.g., those listed in Speel et al, Textile Chemicals and Auxiliaries, 2nd Edition; Reinhold Publishing Corporation, 1957. Some ethoxylated alcohols are further known to be useful in textile lubricating compositions in combination with quaternary ammonium materials (See Cohen et al, U.S. Pat. No. 3,773,463, issued Nov. 20, 1973).
The use of various sorbitan ester compounds or derivatives as softeners, antistatic agents and auxiliary textile conditioners other than in an automatic clothes dryer is known. (See Atlas Powder Company Bulletin -9, "Industrial Emulsions with Atlas Surfactants," 1953; Crossfield, U.S. Pat. No. 3,827,114, issued Aug. 6, 1974; Karg, U.S. Pat. No. 3,652,419, issued Mar. 28, 1972; Simon et al, U.S. Pat. No. 2,665,443, issued Jan. 12, 1954 and Eisen, U.S. Pat. No. 2,461,043, issued Feb. 8, 1949.) Softening compositions for use in aqueous media comprising (among other components) a quaternary ammonium compound and a sorbitan ester are disclosed in Okazaki et al, U.S. Pat. No. 3,793,196, issued Feb. 19, 1974 and Waitkus, U.S. Pat. No. 2,735,790, issued Feb. 21, 1956.
The U.S. Pat. application of Murphy et al, Ser. No. 461,311, filed Apr. 16, 1974, now abandoned in favor of a continuation-in-part application having Ser. No. 543,606, filed Jan. 23, 1975 now abandoned discloses fabric softening articles comprising a major amount of a sorbitan ester softener and anti-corrosion agent and a minor amount of a cationic compound as a melting point modifying agent and auxiliary softener and anti-stat.
The above prior art references relating to sorbitan esters are, for the most part, directed to the aqueous media treatment of yarn during textile processing. Such references do not appear to recognize the particular advantages of these materials as auxiliary softeners, antistatic agents and controlled release aids for use with the common cationic (e.g., quaternary) compounds in dryer-added fabric softeners. Moreover, the references do not suggest the formulation of dryer-added fabric softening articles of the type disclosed herein comprising a dryer dispensing means, a major amount of a cationic softener, and a minor amount of a sorbitan ester. Nor do these references suggest the anti-corrosion, anti-paint softening benefits provided by the particular mixture of materials employed herein in automatic laundry dryers.
Accordingly, it is an object herein to provide superior methods and articles of manufacture adapted for imparting softness and antistatic benefits to fabrics in a clothes dryer.
It is another object herein to provide such fabric softening articles which are easily manufactured on a commercial scale.
It is another object herein to provide dryer fabric softening articles and methods which do not disadvantageously promote softening of dryer drum paint or corrosion of exposed metal dryer drum surfaces.
These and other objects are obtained herein as will be seen from the following disclosure.